Had 4 digits and 3 in the tens place

This could be literally any number in the thousands with 3 in the tens place

The answer is ab3c where it is not multiplication but digits that the variables are holding for any not neccesarily distinct values of a, b and c. This amounts to 900 possibilities because the first number cannot be a 0. If the first number isn't a 0, the second number can be a 0.